//方法一
class Solution {
public:
    int jumpFloorII(int number) {
        if(number <= 0)
            return 0;
        int total = 1;
        for(int i = 1;i < number;i++)
            total *= 2;
        return total;
   }
};
//方法二
class Solution {
public:
    int jumpFloorII(int number) {
        if(number <= 0)
            return 0;
        return 1<<(number-1);
    }
}；